Can I reuse unmarked stamps.com printed stamps?

Once in a while I receive letters with unmarked printed stamps. Looks like these stamps have been printed online from stamps.com site. I wonder if I can reuse them since they are totally unmarked (don’t appear to have been canceled)?

That’s where they put the hardcore criminals, like those that cut the tags off their mattresses.

The Mattress Police had a huge sting operation in my neighborhood recently. They rounded up dozens of people who cut off their mattress tags. They’re serving time in San Quentin Prison. The Matters Police also confiscated the contraband mattresses. The offenders do get to sleep on these mattresses, but the prison keeps the mattresses when they’re released to offset the costs of their incarceration. The prison has cut their mattress costs down to zero with this program.